Solar water harvesting device

ABSTRACT

A water harvesting device is disclosed. The water harvesting device comprises a thermoelectric module adapted to be provided with an enclosure/container and work on electricity received from an electric power source. A cold plate/sink is provide to condense water available in the hot and humid air. A heat sink is provide with the enclosure/container for exiting heat from the enclosure/container. A spacer is provided between the cold plate/sink and the thermoelectric module such that to reduce the thermal conduction from the hot side to the cold side and to avoid reduction of effectiveness of the thermoelectric module. An inlet is provided at top end of the enclosure/container to allow entry of the hot and humid or ambient air into the enclosure. A container is provided below the cold plate/sink for collecting clean water therein. An outlet is provided near the bottom end of the container to facilitate exit of clean water.

FIELD OF THE INVENTION

This invention relates to a solar water harvesting device. Specifically this invention relates to a device working on solar energy in order to harvest water from hot and humid air and/or ambient air. The water so harvested may be used as drinking water.

BACKGROUND OF THE INVENTION

Although three fourth of the area of total land worldwide is covered with water, but drinking water is not available easily in some areas. Therefore, water harvesting devices are used to harvest water from hot and humid air and/or ambient air. A water harvesting device, disclosed in the U.S. Pat. No. 6,684,648B2, comprises a housing. Condensation means for condensing water vapour entrained in humid and high temperature ambient air. Initial transportation means for transporting by gravity the condensate from said water condensation means. Vent means for facilitating water flow in said apparatus by gravity under ambient pressure. Water preparation means for preparing the water for drinking. Water distribution means for distributing drinking water from said water preparation means by gravity. First control means for controlling the operation of said condensation means and electric means for supplying electric power to operate said condensation means.

Another water harvesting device, disclosed in the U.S. Pat. No. 6,828,499B2, comprises a photovoltaic panel to gather solar energy during daylight hours. Said photovoltaic panel having a light-receiving/condensation surface on which light falls during daylight hours and on which surface atmospheric moisture can condense. An energy-storing member which stores energy converted from said solar energy by said photovoltaic panel during daylight hours and a cooling system that is affixed to said photovoltaic panel so as to cool said light-receiving/condensation surface. Said cooling system is powered by said energy-storing member, wherein said energy-storing member powers said cooling system to cool said light-receiving/condensation surface during periods in the diurnal cycle during which relative humidity is increased, whereby condensation of atmospheric moisture on said light-receiving/condensation surface is enhanced and water formed thereby can be gathered.

There are disadvantages associated with the prior art. One of the disadvantages is that the conventional water harvesting device work only in the areas where electric supply is present.

Another disadvantage is that as the photovoltaic panel is secured with the fixed stand and therefore cannot gather sufficient solar energy and therefore the device cannot work for a required time and thus drinkable water is harvested sufficiently as per the requirement of the user of the device.

Yet another disadvantage is that the conventional devices are costly and maintenance of such devices is also a costly affair.

Therefore, there is a need to invent a solar water harvesting device which can work for a longer time and in the remote areas where electric supply in not available.

ADVANTAGES OF THE INVENTION

Therefore, an object of the present invention is to provide a solar water harvesting device which obviates the disadvantages associated with the prior art.

Another object of the present invention is to provide a solar water harvesting device which is capable to be operated in the remote areas where electric supply is not present.

Yet another object of the present invention is to provide a solar water harvesting device capable to tap the solar energy at all time during the day time and thus it can work for a longer time to produce/harvest drinking water.

Still another object of the present invention is to provide a solar water harvesting device which cheap in cost and maintenance thereof is easy.

A further object of the present invention is to provide a solar water harvesting device capable of recycling energy as the cooled air which is used to condense out the water is then used on the hot side of the thermoelectric to increase its efficiency of cooling.

STATEMENT OF THE INVENTION

According to this invention there is provided a solar water harvesting device comprising a thermoelectric module 102 adapted to be disposed into an enclosure 105 and energized by an electric power source, a cold plate 104 and a heat sink 103 being accommodated in the enclosure 105, a spacer 109 provided between the cold plate and the thermoelectric module such that to reduce the thermal conduction from the hot side to the cold side and to avoid reduction of effectiveness of the thermoelectric module 102, an inlet 111 provided at top end of the enclosure 105 to allow entry of the hot and humid or ambient air into the enclosure, a container 113 being provided below the cold plate 104 for collecting clean water droplets therein, an outlet being provided near the bottom end of the container to facilitate exit of clean water.

BRIEF DESCRIPTION OF THE DRAWINGS

A solar water harvesting device, according to a preferred embodiment of the present invention, is herein described and illustrated in the accompanying drawings wherein;

FIG. 1—illustrates sectional view of a water harvesting device according to an option of the present invention,

FIG. 2—illustrates a solar electric generator,

FIG. 3—illustrates a panel movement flow chart,

FIG. 4—illustrates sectional view of the water harvesting device according to another option of the present invention,

DESCRIPTION OF THE INVENTION

A solar water harvesting device is herein described with numerous specific details so as to provide a complete understanding of the invention. However these specific details are exemplary details and should not be treated as the limitation to the scope of the invention. Throughout this specification the word “comprise” or variations such as “comprises or comprising”, will be understood to imply the inclusions of a stated element, integer or step, or group of elements, integers or steps, but not the exclusions of any other element, integer or step or group of elements, integers or steps.

Referring to the drawings, particularly FIG. 1, sectional view of a water harvesting device is shown. The water harvesting device 101 comprises a thermoelectric module 102 for harvesting water from warm and moist air provided between a heat sink 103 and a cold plate 104 (vertical plate with hydrophobic coating). The thermoelectric module 102, heat sink 103 and cold plate 104 are disposed in an enclosure 105. The enclosure 105 is divided into two parts constituting upper half as a cold side and lower half as a hot side. When DC voltage from an electric power source, for example, DC voltage produced by the solar electric generator (see FIG. 2) is applied to the thermoelectric module 102, it pumps heat from the cold side (left side of upper half of the enclosure 105) to the hot side (right side of lower half of the enclosure 105). The heat sink 103, comprising a heat pipe 106, heat exchange fins 107 and a blower 108, is provided on the hot side of the enclosure 105 such that to reject the heat. A spacer 109, along with a plate 110 made of a thermal interface material provided therewith, is provided on the cold side of the thermoelectric module 102 such that to reduce the thermal conduction from the hot side to the cold side of the thermoelectric module 102 so as to avoid reduction of the effectiveness of the thermoelectric module 102. When the warm and moist air/ambient air 111 comes in contact with the cold plate 104, which is below the dew point, water condenses out of the air. This water then drips from the cold plate/surface 104 in the form of droplets 112 and is collected in a container 113, provided below the cold plate 104, for consumption as clean water. An inlet 111 is provided at the top end of the enclosure for allowing entry of the hot and humid or ambient air into the enclosure 105. When the ambient air come in contact with the cold surface of the cold plate 104 it become colder and this cold air is then blown over the hot side of the thermoelectric module and make the module 102 more effective in removing heat and thus making the water harvesting device more efficient. In one embodiment, the cold plate 104 may be coated with a hydrophobic surface so as to improve the condensation of the hot air significantly and to convert the moist air into water droplets. The cold plate 104 is secured with the thermoelectric module 102 at the cold side thereof.

Referring to FIG. 2, solar electric generator is shown. The solar electric generator comprises an array of solar panels 114 mounted on a frame/structure 115. The frame structure 115 is mounted, rotatably, on support legs 116 provided on either sides of the frame structure 115. Optical sensor 117 is provided on either sides of the frame structure 115 such that to track angle of the sunlight/sun rays relative to the solar panels 114 and if the angle is not normal, the controller (not shown) gives signals to switch on a servo motors 118 provided at one side of the frame 115 so as to rotate the frame 115 by a fixed angle to bring the solar panels 114 in the line of the sunlight. The optical sensor 117, checks again (see FIG. 3) if the sunlight is falling onto the surface of the solar panels 114 directly or not, if not then the controller switch on the servo motor 118 again till the sunlight fall onto the solar panels 114 directly at a right angle. Thus, the sun rays are incident substantially onto the photovoltaic cell surface of the solar panels 114. The solar panels 114 provide DC electric power to the thermoelectric module 102 directly through a pair of cables 119 (see FIG. 1). The thermoelectric module 102 is configured to run at the voltage output of an electric power source, for example, solar panels 114 of solar electric generator. Therefore, charge controller, electric battery and inverter (DC-AC) are not needed and thus the cost of the water harvesting device is minimized.

Referring to FIG. 4, sectional view of a water harvesting device, according to another embodiment, is shown. The water harvesting device comprises a thermoelectric module 120 provided at one side of an enclosure/container 121 and for harvesting water from warm and moist air provided between a cold sink 122 and a heat sink 123. The thermoelectric module 120 is connected with the power source, for example, a solar electricity generator. The heat sink 123 comprises a heat pipe 124 having fins 125 provided at one end thereof. In this embodiment the cold sink 122 is provided within the container 121 and the heat sink 123 is provided outside the enclosure/container 121 such that to eject the heat from the container 121. A spacer 126 is provided between the clod sink 122 and thermoelectric module 120 such that to reduce the thermal conduction from the clod sink 122 to the thermoelectric module 120 and thus to avoid reduction of the effectiveness of the thermoelectric module 120. When the warm and moist air comes in contact with the cold sink 122 which is below the dew point, water condenses out of the air and collected in the container 121 for consumption as clean water. An inlet pipe 127 is provided at top end of the enclosure/container 121 to allow entry of the ambient air inside the container 121. An outlet 128 is provided near the bottom end of the container 121 to facilitate exit of clean water as and when required.

In this embodiment the heat sink 123 is provided on the cold side, that is outer side of the container 121. The heat sink 123 may also be replaced with a plate like structure. In one embodiment, the heat sink 123 can also be coated with a hydrophobic material such as Teflon. The cold air is sucked via a fan 129 and is thrown out through the heat sink 123. A partition (not shown) is provided on the interior of the container 121 to ensure that the air that is getting sucked in the cold side of the enclosure/container 121 is forced to go over the cold sink 122 so that it get cooled. This cold air is then used on the hot side of the thermoelectric module 120 to provide cooling effect there.

In both the above mentioned embodiments, the spacer 109/126 is provided on the cold side, respectively. The spacer 109/126 is preferably made of the same material as that of the heat sink 103 or the plate 104 which is of high thermal conductivity material such as aluminum or copper. To get good heat transfer between the two sides of the thermoelectric module 102/120 the hot side heat sink and the cold side heat sink, a thermal interface material (TIM) is provided between the thermoelectric module 102/120 surface and the respective heat 103/123 sinks plates. For TIM to have low thermal resistance, good amount of pressure is required. This is provided by having a set of four screws 130 (see FIG. 1) which bind the hot sink 103, the thermoelectric module 102, the spacer 109 and the cold side heat sink 104 together. In order to minimize thermal conduction between the hot side and the cold side heat sink, two different embodiments are provided. In one of the embodiment, the whole screw is made out of very low thermal conductivity material such as nylon as against stainless steel, mild steel or aluminum. According to another embodiment/option grommet 131 along with a metallic bolt is used on the cold side 104 such that there is no metal to metal contact between the two sides of the thermoelectric module.

Like any refrigeration system, the Coefficient of Performance (COP) of the system is a function of the temperature difference across the thermoelectric module's hot and the cold side. Since the cold side temperature needs to be a few degree Celsius below the dew point, and the hot side needs to be above the ambient temperature (to be able to reject the heat from the hot side of the thermoelectric module), it is important to keep the temperature rise on the hot side to be as small as possible. This low temperature rise on the hot side of the thermoelectric module ensures that the thermoelectric module works efficiently and effectively. This is enabled in both the embodiments discussed in this patent by utilizing heat pipes. The heat pipes enable the heat from the hot side of the thermoelectric module to be taken to a larger area where more space is available to provide a multitude of fins over which air flow is provided by means of a fan. Just like the thermoelectric modules, the fan also is powered directly be the DC power output from the same solar panels as described earlier. To decrease the temperature rise on the hot side even further, the dry and cold air generated on the cold side of the thermoelectric is directed via the fan to flow over the hot side heat sink. In a heat pipe, the highest thermal resistance is encountered over the evaporator section. Since this resistance is inversely proportional to the area available for evaporation, it is important to maximize the evaporator area over the heat source (i.e. the hot side of the thermoelectric module). This is enabled by using a multitude of heat pipes which are flattened on the evaporator end so they can be attached to a metallic plate by soldering to it. A thermal interface material, as described earlier, is used between the heat pipe assembly and the thermoelectric device. In order to get good performance of thermal interface material, a hacking plate is used with the heat pipe assembly though which the earlier described screws (metallic screws with a plastic grommet or non-metallic screws) are used to minimize back flow of heat. The whole assembly comprising of the backing plate, heat pipe assembly, thermal interface material, thermoelectric module, another thermal interface material, cold side spacer and the cold sing (or cold plate) is held in place by these screws.

Certain features of the invention have been described with reference to the example embodiments. However, the description is not intended to be construed in a limiting sense. Various modifications of the example embodiments as well as other embodiments of the invention, which are apparent to the persons skilled in the art to which the invention pertains, are deemed to lie within the spirit and scope of the invention. 

We Claim:
 1. A water harvesting device comprising a thermoelectric module 102 adapted to be disposed into an enclosure 105 and energized by an electric power source, a cold plate 104 and a heat sink 103 being accommodated in the enclosure 105, a spacer 109 provided between the cold plate and the thermoelectric module such that to reduce the thermal conduction from the hot side to the cold side and to avoid reduction of effectiveness of the thermoelectric module 102, an inlet 111 provided at top end of the enclosure 105 to allow entry of the hot and humid or ambient air into the enclosure, a container 113 being provided below the cold plate 104 for collecting clean water droplets therein, an outlet being provided near the bottom end of the container to facilitate exit of clean water.
 2. The water harvesting device as claimed in claim 1, wherein electric power source comprise, for example, a solar electricity generator.
 3. The water harvesting device as claimed in claim 1, wherein the cold plate comprises a vertical plate coated with a hydrophobic coating to provide more cooling effect and is secured with the thermoelectric module at the cold side thereof having a spacer there between.
 4. The water harvesting device as claimed in claim 1, wherein the enclosure is divided into two parts constituting upper half as a cold side and lower half as a hot side.
 5. The water harvesting device as claimed in claim 1, wherein the heat sink comprises a heat pipe having plurality of heat exchange fins provided at one end thereof and a blower being provided such that eject the hot air from the enclosure.
 6. The water harvesting device as claimed in claim 1, wherein the spacer has a plate, made of a thermal interface material, provided therewith such that to remain on the cold side of the thermoelectric module.
 7. A water harvesting device comprising a thermoelectric module 120 adapted to be secured at one side of a container 121 and energized by an electric power source, a cold sink 122 adapted to be disposed in the container being provided for condensing water available in hot and humid air, a heat sink 123 being provided with the container such to remain outside of the container, a spacer 126 provided between the cold sing and the thermoelectric module such that to reduce the thermal conduction from the hot side to the cold side and to avoid reduction of effectiveness of the thermoelectric module 120, an inlet 127 provided at top end of the container to allow entry of the hot and humid air into the container, an outlet being provided near the bottom end of the container to facilitate exit of clean water.
 8. The water harvesting device as claimed in claim 7, wherein electric power source comprise, for example, a solar electricity generator.
 9. The water harvesting device as claimed in claim 7, wherein the cold sink comprises a cold pipe having fins throughout its length and adapted to be secured with the thermoelectric module.
 10. The water harvesting device as claimed in claim 7, wherein the heat sink comprises a heat pipe having plurality of heat exchange fins provided at one end thereof and a blower adapted to be provided on the hot side of the enclosure such that to eject heat from the enclosure.
 11. The water harvesting device as claimed in claim 7, wherein the container is provided to contain condensed water in the bottom end thereof. 